I have set up a private DNS zone and there I have searched through the internet to setup the zone correctly (SOA, NS, A and other record types). There is no delegation from a overlying DNS zone to my zone and so there does not exist any hierarchy. For privacy reason I will call my domain home.local. So the zone looks like this
@ IN SOA primary.home.local. master.home.local. (zone parameter) @ IN NS primary.home.local. primary.home.local. IN A 192.168.1.2
Now because of the fact that the DNS server is only available in my private network and no overlying DNS server needs to delegate any requests to my server, in my opinion the NS record is unneccessary, unless some application does an explicit query for the authoritative nameservers of the zone. If there would be a delegation from the "local." zone then the NS record has to be stored in this zone together with a "A" glue record with the IP address of the nameserver "primary.home.local". But this is not the case und so the NS record seems to me pretty useless and only has some kind of declarative character or am I wrong?